Quantum processes lead to the appearance of mutations in the structure of DNA

(ORDO NEWS) — Scientists have shown that quantum processes play a role in the occurrence of spontaneous mutations in the process of DNA duplication. The proton tunnels along the hydrogen bond connecting the DNA strands, and when they separate, it can end up on the wrong side. This, in turn, threatens to cause mutation.

Replication is the process of doubling a DNA molecule necessary for the transfer of genetic information during cell division.

It runs with amazing accuracy, but errors still occur and sometimes lead to mutations. Using computer simulations, scientists from the University of Surrey (UK) have shown that replication errors can occur due to quantum processes.

DNA is made up of four types of nitrogenous bases: adenine, guanine, thymine, and cytosine. The bases of the two strands of the DNA helix are connected to each other by hydrogen bonds through hydrogen atoms. In this case, adenine is always associated with thymine by two bonds, and cytosine with guanine by three.

The change in these bonds, which occurs during the modification of bases, can lead to the combination of a nitrogenous base with a different pair, which causes mutations.

Although this event was predicted by DNA discoverers James Watson and Francis Crick, only now computer simulations have helped to quantify the likelihood of such a process.

It turned out that the modification of bonds between DNA strands is much more common than previously thought. The nucleus of a hydrogen atom consists of a single proton, which can easily jump over the energy barrier from one side of the hydrogen bond to the other.

This is due to a well-studied quantum process – tunneling, in which a particle (in this case, a proton) overcomes a potential barrier, but its total energy is less than the barrier height. Such a phenomenon, reminiscent of the teleportation of an object through a wall, is of a purely quantum nature and is impossible in classical mechanics.

However, the local cellular environment becomes the cause of the quantum behavior of protons. They are thermally activated and overcome the energy barrier.

So within DNA, protons are constantly tunneling back and forth along the hydrogen bonds between the strands. When separating strands for copying during replication, some of the protons may not be on their side, and this will lead to an error and a base mismatch in the new pair.

Previously, biologists believed that such quantum processes are not able to take place in a warm and complex living cell, and tunneling is possible only at low temperatures in relatively simple systems. Quantum effects in DNA have hardly been considered, but now scientists have shown that they make a big contribution to biological processes.

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